Infancy Physical Development: Motor Development

Angela Oswalt, MSW

Infants need to learn how to move and to use their bodies to perform various tasks, a process better known as motor development. Initially, babies' movements are simply the uncontrolled, reflexive movements they are born with. Over time, they learn to move their body parts voluntarily to perform both gross (large) and fine (small) motor skills. In general, babies begin developing motor skills from the center of the body outward and from head to tail. They learn to control their head and neck before they learn to maneuver their arms; they learn to maneuver their arms before they learn to manipulate their fingers. Babies learn to move their torso before they learn how to move their arms and legs.

As babies learn skills and tasks, they will build new skills on top of old skills. It is important to remember that each child is unique. There is a general sequence of milestones or developmental markers that children achieve, but each child will progress through them at different rates, ages, and sequences. This article will often list ages at which children reach certain milestones. It's important to remember that these are only estimates; children attain or achieve them at a wide and healthy range of ages.

When babies are born, they are equipped with a set of reflexes, or automatic actions. Some reflexes help them perform basic tasks, such as breathing freely and drinking milk, while other reflexes seem to have no real purpose. All of these reflexes can help doctors assess babies for any neurological problems at birth and as they grow. As infants mature in the first few months of life and begin developing the ability to voluntarily move and use their bodies, most of these reflexes gradually and naturally fade away. This article will review seven of the most prominent reflexes babies have: sucking, head turning, rooting, grasping, stepping, Moro response, and tonic neck.

The sucking reflex allows babies to drink milk and nourish themselves in the first days of life. This is a permanent ability, but as babies grow, they can control when they drink. Another permanent and life-supporting reflex is head turning. This reflex allows a baby to turn his head if something (a blanket, pillow, or stuffed animal) is blocking his airflow. Another reflex that also helps babies survive is the rooting reflex. When babies root, they may nuzzle their face and mouth into the caregiver's chest or shoulder. This may help them find a food source, such as their mother's breast; this helps the baby communicate to caregivers that they are hungry and ready to eat. Rooting disappears around 3 weeks of age.

The rest of the reflexes have less survival value but are still notable. For the first 3 to 4 months, babies have an amazing grasping ability and reflex. They will grasp anything placed in their palm and hold it with amazing strength for their size; some infants in the first weeks of life can support their entire body weight through that grasp. While this reflex may not have any survival function in modern times, it does help babies bond with caregivers and family in the first weeks of life. Similarly, for the first two months, babies will "step" with their legs if they are held vertically with their feet touching a surface. Even though this reflex disappears months before babies begin walking purposefully, experts believe stepping helps infants learn how their legs work and can be used. The Moro response is another reflex that is present during the first 6 months of life, but doesn't seem to have a purpose in modern life. A baby will arch her back, flail out, and then curl up if she feels as though she is being dropped. The final reflex this article will mention is the tonic neck. During the first 4 months, when babies lie awake on their backs with their heads facing to one side, they will extend the arm on the side of their body that they're facing and flex the other arm at an angle, in a position that resembles a fencing pose. This reflex may help prepare them for voluntary reaching later in their development.